(1) Field of the Invention
The present invention generally relates to electrical devices such as television signal receivers, and more particularly, to a technique for protecting a memory included in such a device from being inadvertently written to when, for example, signal control lines connected to the memory are shared between different devices.
(2) Description of the Related Art
Electrical devices such as television signal receivers often include one or more circuit boards. Each circuit board typically has attached thereto electrical components, such as integrated circuits (“ICs”) and other elements, which enable various device operations to be performed. Prior designs for television signal receivers often employed only a single circuit board. With these prior designs, a primary incentive was to maximize the use of board area. However, since only one circuit board was used, no issues regarding connections between different circuit boards existed.
Current designs for television signal receivers, on the other hand, may use multiple circuit boards. The use of multiple circuit boards, as compared to a single board, is particularly attractive since it enables the circuit design to be modularized. In particular, different board sections can be re-designed without having to reorganize the layout of all receiver circuits, as is often the case when using only a single circuit board. Moreover, the use of multiple circuit boards allows a single-sided board to be used for one group of circuits, and a multi-layer board for other circuits.
Despite its advantages, the use of multiple circuit boards does create disadvantages regarding connections between different boards. In particular, it is desirable to minimize the number of connectors (e.g., pins) used to provide a connection between circuit boards. Minimizing the number of such connectors is especially desirable since the cost of each connector is quantifiable in a monetary sense. This is particularly significant in certain industries, such as the consumer electronics industry, where product cost is a driving force among competitors. Accordingly, there is a need for a technique which reduces the number of connections required between circuit boards in an apparatus, such as a television signal receiver.
One such technique for reducing the number of connections between circuit boards involves sharing signal control lines connected between two circuit boards of an apparatus, such as a television signal receiver. According to this technique, a microcontroller on one circuit board uses the signal control lines to read a memory on another circuit board when the apparatus is placed in the OFF state, and uses the same signal control lines to control another operation of the apparatus (e.g., a deflection operation) when the apparatus is placed in the ON state.
In practicing the aforementioned technique, a problem has been identified in that the memory may be inadvertently written to when the microcontroller uses the signal control lines to control an apparatus operation while the apparatus is placed in the ON state. Accordingly, there is a need for a technique that enables the signal control lines to be shared, but prevents the memory connected to the lines from being inadvertently written to by the microcontroller, or other devices connected to the control lines. The present invention addresses these and other issues.